class Solution {
public:
    string tree2str(TreeNode* root) {
        if(root ==nullptr)
            return string();
        string str;
        str+=to_string(root->val);
        if(root->left)
        {
            str+='(';
            str += tree2str(root->left);
            str +=')';
        }
        else if(root->right)
        {
            str+="()";
        }
        if(root->right)
        {
            str+='(';
            str += tree2str(root->right);
            str +=')';
        }
         return str;
    }
   
};